4-Deoxy-D-fructose-6-phosphate

Guerard, G., Alphand, V, Archelas, A., Demu5mck, G., Hecquet, L., Furstoss, R. and Bolte, J. (1999) Transketolase-mediated synthesis of 4-deoxy-D-fructose 6-phosphate by epoxide hydrolase-catalysed resolution of l,l-diethoxy-3,4-epoxybutane. Eur. J. Org. Chem., 3399 402. 

In a very imaginative piece of research Frost and coworkers have developed a plasmid-based method for synthesizing aromatic amino acids, by incorporating the genes that code for the enzymes that perform the series of conversions from D-fructose-6-phosphate to D-erythrose-4-phosphate to 3-deoxy-D-arabinoheptulosonic acid-7-phos-phate (DAHP) near each other on a plasmid that can be transformed in E. coli. The enzymes are the thiamin diphosphate-dependent enzyme transketolase in the nonoxida-tive pentose shunt and DAHP synthase. The DAHP is then converted to the cyclic dehydroquinate, a precursor to all aromatic amino acids L-Tyr, L-Phe and L-Trp165,166 (equation 27). 

Prokaryotic organisms synthesise a primary form of vitamin pyridoxol 5 -phosphate from 1-deoxy-D-xylulose 5-phosphate (l-deoxy-D-t/treo-pent-2-ulose 5-phosphate) and 2-amino-2-deoxy-D-threo-tetronic (2-amino-2-deoxy-D-threonic) acid, known as 4-(phosphohydroxy)-L-threonine or 4-hydroxy-i-threonine 4-phosphate. Phosphohydroxythreonine arises from D-erythrose 4-phosphate, a product of decomposition of D-fructose 6-phosphate. Non-phosphorylated forms (pyridoxal, pyridoxol and pyridoxamine) are produced by hydrolysis of the corresponding phosphates. Animals do not synthesise vitamin Bg de novo, only convert the non-phosphorylated forms in the Hver, erythrocytes, and other tissues into the corresponding phosphates and the individual forms of each other. Pyridoxal 5 -phosphate arises by oxidation of pyridoxol 5Lphosphate and transamination of pyridoxal 5 -phosphate provides pyridoxamine 5Lphosphate. Both these forms of vitamin Bg are catalytically active. Pyridoxal 5 -phosphate... 

Fig. 2 Representation of the sugar to PHA metabolism in Burkholderia sacchari. Adapted from Lopes et al. (2011) and Lopes et al. (2010) G6P glucose 6-phosphate, 2KDPG 2-keto-3-deoxy-6-phosphogluconate, G3P D-glyceraldehyde 3-phosphate, PEP phosphoenolpyruvate, PYR pyruvate, rbSP rlbulose-5-phosphate, RbSP rlbose-5-phosphate, X5P xylulose 5-phosphate, S7P sedoheptulose 7-phosphate, F6P fructose 6-phosphate, E4P erythrose 4-phosphate, AcCoA acetyl-coenzyme A)...

The 3-deoxy-D-ara6mo-2-heptulosonic acid 7-phosphate (DAHP) synthetase (EC 4.1.2.15) is an enzyme involved in the shikimic pathway of aromatic amino acids biosynthesis in bacteria and plants, where catalyzes the construction of 3-deoxy-D-ara6/ o-2-heptulosonic acid 7-phosphate from phosphoenolpyruvate and D-erythrose 4-phosphate [6]. Although 3-deoxy-D-ara6/H0-2-heptulosonic acid 7-phosphate (DAHP) synthetase has not been widely investigated it has been employed for the DAHP synthesis on preparative scale from D-fructose in multienzyme system [68], This one-pot synthesis was subsequently even more simplified by the results of further studies which indicated that it was more efficient and economical to use the whole cells containing a DAHP synthetase plasmid [69]. 

We have developed preparative enzymatic syntheses of several unusual hexoketoses using fructose-1,6-diphosphate aldolase (FDP-aldolase, E.C.4.1.2.13) as catalyst and dihydroxyacetone phosphate (DHAP) and an aldehyde as substrates (15). The enzyme appears to be very specific for DHAP but will accept a variety of aldehydes as acceptors. The ketose-1-phosphates prepared are converted to the phosphate free ketoses after removal of the phosphate group by acid- or phosphatase-catalyzed hydrolysis. The ketoses can be isomerized stereospecifically to aldoses catalyzed by glucose isomerase (E.C.5.3.1.5.) from Flavobacteriuum arborescens. The equilibrium mixtures of aldoses and ketoses are then separated by chromatography on Dowex 50 (Ba ) or Dowex 1 (HSO "). Figure 1 illustrates the preparation of a mixture of 6-deoxy-6-fluoro-D-fructose... 

Monosaccharides. M. are linear polyhydroxyalde-hydes (aldoses) or polyhydroxyketones (ketoses). Most important among M. are the pentoses (CjHiqO,) and hexoses (C6H,20 ). Important aldopentoses include, e.g., D- ribose, D- xylose, and L- arabinose. Important aldohexoses include D- glucose, D- man-nose, and D- galactose the major ketohexoses are D- fructose and sorbose. The 6- deoxy sugars L- fu-cose and L- L-rhamnose are also widely distributed hexoses. M. with more carbon atoms (heptoses 7 carbon atoms, octoses, etc.) or less carbon atoms (trioses 3 carbon atoms) do not occur in the free form in organisms but do play a role in carbohydrate metabolism as phosphate esters tetroses (4 carbon atoms) erythrose, threose are relatively rate. 

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